current research
Carbon Monoxide in Detroit, New York, and Los Angeles Air Joseph M. Colucci and Charles R. Begeman General Motors Research Laboratories, Warren, Mich. 48090
w Atmospheric carbon monoxide concentrations measured at 12 street level locations were generally about 50% higher in Los Angeles than in Detroit or New York. They were highest in commercial areas, intermediate in freeway areas, and lowest in residential areas. The highest concentrations were at Pic0 Boulevard, Los Angeles: 38 p.p.m. for 1 hour, 27 p.p.m. for 8 hours, and 17 p . p m for 24 hours. The highest weekday average concentration was 10.5 p.p.m. at Herald Square, New York. Minimum concentrations were 1 p . p m at nine sites and 2 p.p.m, at three sites. Average concentrations on weekends were about 20z lower than on weekdays. Concentrations were generally highest in autumn and lowest in spring, reflecting an inverse relationship with wind speed. Atmospheric carbon monoxide concentrations correlated closely with traffic density in Detroit and New York, but less closely in Los Angeles
A
tmospheric concentrations of carbon monoxide in the Detroit, New York, and Los Angeles metropolitan areas were measured as part of a program to determine the relationship between automotive traffic and airborne carcinogenic material (Begeman and Colucci, 1962; Colucci and Begeman, 1965). Although the sampling program was not specifically organized as a survey of carbon monoxide in city air, the results are reported separately because of the current interest in atmospheric carbon monoxide concentrations. Experimental Apparatus. Atmospheric carbon monoxide concentration was measured with a Beckman Model 21 nondispersive infrared analyzer equipped with an 89-cm. sample cell. Cell pressure was 2.8 kg. per sq. cm., and flow rate was nominally 1500 cc. per minute. The sample was dried with molecular sieve 4A (Linde) because carbon monoxide-free air at 20" C., 65 relative humidity (a not unusual condition), caused a response equivalent to 5 p.p.m. of carbon monoxide. The apparatus (Figure 1) was installed in a panel truck which was parked with the engine off during sampling. The sample intake was about 1.5 meters above ground at the rear of the truck. Electrical power (115-volt, 60-Hz.) for the apparatus was obtained from external sources. Prior to the start of sampling, the infrared analyzer was warmed up for several hours. The apparatus was calibrated at the start of a sampling operation and once or twice per day
thereafter. Prepurified nitrogen was used as a zero gas, and 20to 40-p.p.m. carbon monoxide blends in prepurified nitrogen were used as upscale standards. Measured carbon monoxide concentrations are considered accurate to + 5 % , or 0.5 p.p.m., whichever is greater. The analyzer output was continuously recorded by a strip chart recorder connected to a Perkin-Elmer Model 194 printing integrator. The average carbon monoxide concentration, equivalent to the area under the recorder trace, was obtained from the integrator output tape. Quarter-hour digitized readings were used in a computer program to calculate 15-minute and hourly average concentrations. One- and 5minute averages were determined from the strip chart recording. Sampling Sites. The 12 sampling locations in the Detroit, New York, and Los Angeles metropolitan areas are described in Table I. Traffic at the sites covered a wide range in terms of car density and speed-for example, measurements were made at commercial or downtown areas, where traffic density was high, and mostly stop-and-go at low speed; freeway (expressway) areas, where traffic density and average speed were generally high; and residential areas, where traffic density was generally low, and speeds were moderate or low. At several sites the truck was parked on city streets as close as 2 meters to local traffic. Most of the sites were less than 20 meters from traffic, but one was 150 meters from traffic. Although the sites in the several cities are designated according to a certain area characteristic-Le., freeway, commercial, and residential-the distinctions are not cleancut. For example, at the Queens Expressway Interchange, designated a freehay site, the sampling vehicle was located about 75 meters southwest of and 10 meters above the freeway, on a residential street about 400 meters east of a commercial street, Queens Boulevard. .,!.,Ybh .~
_- ,.
-'L
G?A.,\C.
-roc
Figure 1. Carbon monoxide measuring system Volume 3, Number 1, January 1969 41
Table I. Sampling Times and Sites Metropolitan Area and Sampling Period Detroit, Aug. 1961 to Feb. 1964
New York, April 1962 to Feb. 1964
'
Site John Lodge-Edsel Ford Freeway Interchange Grand Circus Park
1001
728
273
Commercial
General Motors 1261 Technical Center, Warren Detroit area totals 3449 Herald Square, 446 Manhattan
968
293
Residential
2562 398
887 48
Commercial
253
197
56
Commercial
496
382
114
Freeway
Queens residential
105
105
...
Residential
Scarsdale, WestChester County New York area totals Pic0 Boulevard
135
135
...
Residential
1435
1217
21 8
1090
766
324
Harbor-Santa Monica Freeway Interchange Santa Monica
23 1
175
56
Freeway
325
277
48
Residential
Monrovia
290
242
48
Residential
1936
1460
476
Columbus Circle, Manhattan Queens Expressway Interchange
Los Angeles, April 1964 to Oct. 1965
Sampling Time, Hours Week- Weekend Area Type Total day 866 321 Freeway 1187
Los Angeles area
Commercial
Specific Location Dead-end street adjacent to northeast side of interchange Southwest corner of parking lot at Madison and Witherell Field at northwest corner of Technical Center
Approximate Distance from Nearest Traffic, Meters 5
5
About 150
Broadway, between 2 34th and 35th Streets Within circle drive, in 3 southeast quadrant 134th St., first street About 75 from expressway, 2 from residensoutheast of interchange parallel to tial traffic Van Wyck Expressway, south of Union Turnpike Northeast corner of 2 185th St. and 90th Ave. Shoulder adjacent to 2 Murray Hill Road
Southwest corner of car storage lot at Pic0 Blvd. and Manhattan Place Car storage lot under elevated interchange
4
Car storage lot at Santa Monica Blvd. at 15th St. Car storage lot at 840 Huntington Blvd.
6
5
20
totals
Sampling in Detroit was initially to check out the apparatus, and later to obtain additional data. In New York and in Los Angeles, on the other hand, sampling was on a quarterly schedule, to evaluate seasonal effects. Individual sampling experiments ranged from 21 to 800 hours, averaged 115 hours, and totaled 6820 hours. About 5 0 z of the sampling time was in Detroit, 20% in New York, and 3 0 z in Los Angeles. Weekday (Monday through Friday) sampling accounted for 77% of the total. Results and Discussion
Concentrations for Various Data Groupings. Average carbon monoxide concentrations are summarized in Table I1 for both weekdays and weekends. The over-all average for Los Angeles was higher than for 42
Environmental Science & Technology
either New York or Detroit. Because sampling sites in all three metropolitan areas are geographically distributed, it may be justifiable to rank carbon monoxide pollution among the three areas in the order of the over-all averages given in Table 11. The much higher frequency of atmospheric temperature inversion in Los Angeles (Hosler, 1961), together with the lower average wind speed, undoubtably contributed to the relatively higher carbon monoxide concentration compared to Detroit and New York. Temperature inversion, which limits the vertical ventilating capacity of the atmosphere, often results in smog in Los Angeles (Leighton, 1961) and in abnormally high carbon monoxide concentrations. For example, between September 21 and October 27, 1965, the average carbon monoxide concentration on 21 smoggy days (as indicated by a 1-hour oxi-
Table 11. Weekday and Weekend Carbon Monoxide Averages Site Detroit area Lodge-Ford Freeway Interchange Grand Circus Park G M Technical Center, Warren Detroit area average New York area Herald Square Columbus Circle Queens Expressway Interchange Queens residential Scarsdale, Westchester County New York area average Los Angeles area Pic0 Boulevard Harbor-Santa Monica Freeway Interchange Santa Monica Monrovia Los Angeles area average Site types Freeway Commercial Residential
Carbon Monoxide, P.P.M. Weekday Weekend
6 3.5 2.5 4
5.5 3 2 3.5
10.5 7.5 3.5 3 2 5
5.5 7 4.5 ...
9
6.5
8 5 5.5 7.5
8 4.5 4 6
6 7.5 3.5
6 5.5
...
Table 111. Seasonal Weekday Carbon Monoxide Averages Carbon Monoxide, P.P.M. Site Spring Summer Autumn Winter New York area Herald Square 8.5 11.5 12 10.5 Columbus Circle 6 9.5 8.5 4 Queens Expressway Interchange 2.5 3 7 2.5 Queens residential 3.5 3 4 3 Scarsdale, WestChester County 1.5 2 2.5 2.5 New York area average 4 5.5 I 4 Los Angeles area Pic0 Boulevard 7 5.5 9 11 Harbor-Santa Monica Freeway Interchange 5.5 7 9 11 Santa Monica 4 4.5 4 6.5 Monrovia 4.5 4.5 8.5 5.5 Los Angeles area average 5.5 5.5 8 10.5 Wind Speed Average.5 Mete& per Second Spring Summer Autumn Winter New York 5.5 4.5 4.5 5.5 Los Angeles 4.5 4 4 3.5 0
dant concentration greater than or equal t o 0.15 p.p.m.) (California Department of Public Health, 1960) was 11.5 p.p.m. at the Pic0 Boulevard site, but only 6 p.p.m. on 16 smogless days. Oxidant concentrations were obtained from Clean Air Quarterly (1965, 1966). The 20% lower average wind speed on the smoggy days might account for part of the higher carbon monoxide average, but most of the difference was probably due to the reduced vertical ventilation under the inversion layer during the smog. Castrop, Stephens, et nl. (1955) measured carbon monoxide as four times higher on smoggy days (visually defined) in Los Angeles than on smogless days. In general, the average carbon monoxide concentration on weekends (Saturday and Sunday) was about 20% less than on weekdays. Only at the freeway sites in New York and Los Angeles did the weekend average equal or exceed the weekday average. Weekend concentrations were not measured at the two New York residential sites, Separation of sites according t o area type (bottom of Table 11) indicates that carbon monoxide concentrations were generally highest in commercial areas, intermediate in freeway areas, and lowest in residential areas. Average concentrations in New York and Los Angeles, separated according t o seasons, are summarized in Table 111. No Detroit results are given because sampling there was not on a seasonal schedule. At four of the five sites in the New York area, the highest concentrations were in autumn and the lowest in either spring or winter. Inasmuch as automobile traffic may be considered fairly constant during the year, it is likely that the higher carbon monoxide levels are associated with lower than average wind speed in summer and autumn (Table 111). Similarly, average concentrations in Los Angeles were highest during the seasons of lower than average wind speed, in this case autumn and winter. The situation in Los Angeles was further complicated by atmospheric inversions. Hosler
Wind speed data from U. S. Dept. of Commerce (1962-196s). 98 MEDIAN CONCENTRATION I N PARENTHESES
0 2
3
4
6
8
IO
CARBON MONOXIDE
15
20
30
40
- PPM
Figure 2. Frequency distribution of weekday hourly average carbon monoxide concentrations at Detroit area sites
(1961) has shown that inversions in Los Angeles occur most frequently in autumn and winter. The per cent time for which the weekday hourly average carbon monoxide concentration was greater than or equal to a given concentration is shown in Figures 2, 3, and 4 for the three metropolitan areas. The distributions are nearly lognormal, with the exception of the Queens Expressway InterVolume 3, Number 1, January 1969 43
99 I 98
95
MEDIAN CONCENTRATION I N PARENTHESES
MEDIAN CONCENTRATION I N PARENTHESES
-
I
\
2
3
IERALD SQUARE 19-1/2
4
6
8
15
IO
CARBON MONOXIDE
-
20
30
PPM)
40
PPM
1
2
3
4
6
8 10
CARBON MONOXIDE
15
20
30
40
- PPM
Figure 3. Frequency distribution of weekday hourly average carbon monoxide concentrations at New York area sites
Figure 4. Frequency distribution of weekday hourly average carbon monoxide concentrations at Los Angeles area sites
change, which seems definitely skewed. The median ( 5 0 x frequency) concentration for each site is indicated on the figures. In general, the median was either equal t o or slightly less than the average concentration. Maximum concentrations for elapsed times ranging from 1 minute to 24 hours are given in Table IV. Minimum hourly concentrations at all sites were 1 or 2 p.p.m. Maximum concentrations at six Continuous Air Monitoring Program stations (Larsen, Zimmer, et al., 1967), included in Table IV, were, in general, about the same as at Herald Square and Pic0 Boulevard. Because the Herald Square and Pic0 Boulevard sites were closer to traffic than the CAMP stations, it is reasonable t o expect higher carbon monoxide concentration at these two sites than at the CAMP stations. However, considerably greater sampling time at the CAMP stations would increase the probability of detecting higher maximum concentrations of carbon monoxide. The combination of distance and time factors might account for the similarity of the results in the two studies. The average carbon monoxide concentrations previously discussed were integrations over relatively long sampling periods. The concentration, of course, varied throughout the day, as noted also by others (Clayton, Cook, et al., 1960; Jacobs, Braverman, et al., 1959; Lawther, Commins, et al., 1962; McCormick and Xintaras, 1962; Moureau, 1964). A typical trace covering 24 hours at the Detroit Freeway Interchange was published (Colucci and Begeman, 1965). Hourly average concentrations as a function of time of day are illustrated in Figures 5,6, and 7 for the Detroit, New York, and Los Angeles sites, respectively. The value for a given hour of the day represents the weekday average for many days at that hour. Morning and late afternoon peaks were prominent at all sites in Detroit and New York, and correspond to the heaviest traffic periods. Peaks were especially distinct at freeway sites.
At commercial sites in both cities the concentration during the middle of the day remained high with respect to the morning and evening peaks. In Los Angeles, the morning peak near 8 A.M. was evident at all sites, and coincided with peak rush hour traffic. However, during the late afternoon traffic rush hour, there was at best only a poorly defined carbon monoxide concentration increase. This situation probably resulted from the greater wind speed in the afternoon, usually about twice the wind speed in the morning. Unusually high carbon monoxide concentrations were fre. quently measured in Los Angeles between 9 P.M. and 2 A.M. when traffic was light. The meteorology and topography of the Los Angeles basin are probably the reason for this situation. During the day, westerly winds from the ocean moved the pollutants into the San Gabriel Valley, east of Los Angeles, from where they were returned at night with a gentle easterly wind. Furthermore, at night the pollutants were kept close t o the ground under the normal nocturnal inversion (Hosler, 1961). During nights when the wind was from the west, carbon monoxide concentrations in Los Angeles were relatively low. High nighttime carbon monoxide levels in Los Angeles were observed also by Bryan and Taylor (1965).
44 Environmental Science & Technology
Carbon Monoxide Concentration and Trafic Density Reluted
To check on the implied relationship between carbon monoxide in air and traffic density, correlation coefficients were calculated between weekday hourly average carbon monoxide concentrations and weekday traffic data. Two different sets of traffic data were used in correlations with carbon monoxide concentrations at the Lodge-Ford Freeway Interchange in Detroit : for total traffic on the freeway system (Detroit Free Press, 1961) and for traffic into the interchange only (Detroit Department of Streets and Traffic,
Table IV. Maximum Carbon Monoxide Concentrations for Various Time Periods Carbon Monoxide, P.P.M. 15 min. 1 hr. 3 hr. 8 hr. 1 min. 5 min. Site Detroit area Lodge-Ford Freeway Interchange Grand Circus Park G M Technical Center, Warren New York area Herald Square Columbus Circle Queens Expressway Interchange Queens residential Scarsdale, Westchester County Los Angeles area Pic0 Boulevard Harbor-Santa Monica Freeway Interchange Santa Monica Monrovia U.S.P.H.S. C A M P stations' Chicago Cincinnati Los Angeles Philadelphia San Francisco Washington, D. C. Q
1
6
--
7 24 hr.
39 58 38
34 28 28
31 17 20
26 15 12
22 12 10
16 10 7
14 8 6
13 6 5
75 38 34 24 19
52 34 32 18 14
42 24 28 12 9
35 22 25 9 6
24 20 21 8 5
22 15 16 6 4
17 14 14 5 3
13 11 11 4 2.5
70 70 60 50
50 31 45 22
40 30 25 20
38 23 20 17
34 21 17 13
27 18 13 11
20 14 9 10
17 13 9 9
...
64 26 81 52 40 44
...
... ... ... ...
...
46 22 47 47 38
...
41
...
35 19 28 35 18 34
... ... ...
... ...
...
... ...
...
I
.
27 17 23 25 14 23
.
... ,..
... ...
...
Larsen, Zimmer, et ai.,1967.
-
III
LODGE-FORD FREEI'IAY INTERCHANGE
G R A N D CIRCUS PART GM TECHNICAL CENTEl, MARREh
PM
AN,
0
' M
2
~ 4
" 6
~ e
l
~ O
N
~ 2
~ 4
6
~ 8
~ IO
~
~
~
M
T I N E CF D A Y
Figure 5. Hourly carbon monoxide concentrations on weekdays at Detroit area sites
1966). In New York City. generalized midtown traffic data (Lieper. 1962) were correlated with carbon monoxide concentrations at Herald Square and Columbus Circle. In addition, simultaneous measurements of carbon monoxide concentration and traffic counts for 42 hours at Herald Square (Greisarian. 1962) were correlated. In Los Angeles, traffic data obtained on the Harbor Freeway (Wilson, 1966) about one mile south of the interchange with the Santa Monica Freeway were correlated with carbon monoxide concentrations measured at the Interchange. Carbon monoxide concentration and traffic density generally varied in a similar manner at each site (Figure 8).
Correlation coefficients between carbon monoxide concentrations and traffic count (Figure 8) ranged from 0.75 t o 0.95. Similar relationships have been noted by others (Clayton, Cook, et al., 1960; McCormick and Xintaras, 1962; Moureau, 1964). In contrast t o the correlation coefficient of 0.95 for generalized midtown traffic and carbon monoxide concentrations a t Herald Square (Figure 8) (398 hours of carbon monoxide measurements), the correlation coefficient between the simultaneous measurements of carbon monoxide concentration and traffic counts at Herald Square (42 hours) was only 0.81. This lower value may be due t o short-term meteorological Volume 3, Number 1, January 1969 45
~
'
TIME OF DAY
Figure 6. Hourly carbon monoxide concentrations on weekdays at New York area sites
zt
1 AM
O M
2
4
6
?4.b
8
IO
N
2
4
6
B
1
0
M
TIME OF DAY
Figure 7. Hourly carbon monoxide concentrations on weekdays at Los Angeles area sites
influences, whereas over longer periods the meteorological effectsmay average out. At the Lodge-Ford Freeway Interchange the correlation coefficient between carbon monoxide concentration and total freeway traffic was 0.92 (Figure S), whereas for traffic into the interchange the correlation coefficient was 0.83. The correlation coefficients seem high, especially when one considers that carbon monoxide concentration and traffic data were, with one exception, not measured simultaneously, and that carbon monoxide emissions vary greatly for different vehicle operating modes. Furthermore, the relationship would not be expected t o apply when traffic is completely stalled and the traffic count is zero, but carbon monoxide emission is relatively high. 46 Environmental Science & Technology
Comparisons with Other Measurements Carbon monoxide concentration averages of this study are compared with the results of other investigators for the same cities in Table V. In Detroit, Clayton, Cook, et al. (1960) measured a carbon monoxide average of 8.5 p.p.m. at a depressed freeway site with a probe located at the curb. This concentration may be contrasted with 6 p.p.m. at 5 meters from the freeway curb in our study. It is reasonable to expect a higher carbon monoxide concentration at the curb than at 5 meters from the curb, as in-car cs. off-road measurements have shown (Brice and Roesler, 1966). At a downtown and a neighborhood shopping site, Clayton, Cook, et a/. (1960) measured carbon monoxide averages of 8.5 and 10.5 p.p.m., respectively. Both
I
I
CA33CU MONOXIDE
about 2 meters from the curb. At other sites Johnson, Dworetzky, et a/. measured carbon monoxide averages lower than those at our Manhattan sites, presumably because their sites were further removed from traffic than ours. Braverman (1967) reported carbon monoxide at a residential site in Manhattan to be similar to that found at our residential site in Queens. However, his site was at the second story of a building, whereas ours was 1.5 meters above ground at curbside. In Los Angeles, Bryan and Taylor (1965) reported carbon monoxide averages about one third higher than we report for similar sites. Part of this difference might be due to water vapor in their samples (Bryan, 1963). Acknowledgment
i
h
The authors appreciate the assistance of John H . Neff, Research Laboratories Fuels and Lubricants Department, in the sampling and data reduction procedures, and Robert W. Lietz, Electronics and Instrumentation Department, in maintaining the carbon monoxide instruments. They also appreciate the assistance of public officials in Detroit and New York. Literature Cited Begeman. C. R.. Colucci. J. M.. Natl. Cuncer Inst. MononraDh g, 15-57 (1962). Braverman, M. M., Am. Ind. H y g . Assoc. Quart. 28, 291-3 (1967). Brice, R. M., Roesler, J. F., J . Air Pollution Control Assoc. 16, 597-600 (1966). Bryan, R . J., J . Air Pollution Control Assoc. 13, 254-65 (1963). Bryan, R. J., Taylor, J. R., 58th Annual Meeting, Air Pollution Control Association, Toronto, Canada, 1965. California Department of Public Health, Berkeley, Calif., "California Standards for Ambient Air Quality and Motor Vehicle Exhaust," 1960. Castrou, V. J., Steuhens. J. F., Patty. F. A.. Am. Ind. Hvn. Ass&: Quart. 16,-225-9 (1955). Clayton. G. D., Cook W. A., Fredrick, W. G., Am. Ind. Hyg. ASWC.J . 21, 46-54 (1960). Clean Air Quarterly (California Department of Public Health, Berkeley) 9, 23 (1965). Ckan Air Quarterly (California Department of Public Health, Berkeley) 10, 19 (1966). Colucci, J. M., Begeman, C. R., J . Air Pollution Control Assoc. 15, 113-22 (1965). Detroit Department of Streets and Traffic, private communication, 1966. Detroit Free Press, 6A (Aug. 13, 1961). Greisarian, J., New York City Department of Traffic, private communication, 1962. Hosler, C. R., Monthly Weather Reu. 89, 319-39 (1961:). Jacobs, M. E., Braverman, M. M., Hochheiser, S., J. Air Pollution Control Assoc. 9, 110-14 (1959). Johnson, K. L., Dworetzky, L. H., Heller, A. N., New York City Department of Air Pollution Control, private communication, 1967; Science 160, 67-8 (1968) (in part). Larsen, R . I., Zimmer, C. E., Lynn, D. A., Blemel, K. G., J. Air Pollution Control Assoc. 17, 85-93 (1967). Lawther. P. J.. Commins. B. T.. Henderson. M.. Ann. Occuuat. Hyg. 5, 24118 (1962). ' Leighton, P. A., "Photochemistry of Air Pollution," p. 2, Academic Press, New York, 1961. Lieper, J. M., Trafic Quart. 16,212-28 (1962). McCormick, R. A., Xintaras, C., J . Appl. Meteorol. 1, 237-43 (1962). Moureau, H., Proc. Roy. Soc. Med. 57,1015-20 (1964). U. S. Dept. Commerce, monthly data and data supplements for New York La Guardia Airuort and Los Angeles International Airport, 1962-1965. Wilson. J. E.. California Deuartment of Public Works. urivate communication, 1966.L
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